1. Field of the Invention
The present invention relates to a manipulator and, more particularly, to a medical manipulator of a simple mechanism excellent in operability.
2. Description of the Related Art
Referring to FIG. 25, when practicing laparoscopic-surgical operation, such as cholecystectomy, some small holes 151, 152 and 153 are formed in the abdomen of a patient 150 and tubes 154 are inserted in the holes 151, 152 and 153. An endoscope 161 and forcepts 171 and 172 are inserted through the tubes 154 in the abdomen. An operator 160, i.e., a surgeon, performs a surgical operation observing images taken by the endoscope 161 and displayed by a monitor 162. Such an operative method does not need laparotomy and reduces physical burden on the patient and reduces greatly the number of days necessary for the patient to recover and to leave the hospital after the operation. However, it is a problem in some cases that the operator 160 is unable to observe a diseased part directly. Furthermore, the forcepts 171 and 172 are provided with only grippers capable of opening and closing, it is difficult to change the attitude of the grippers freely and hence the forcepts 171 and 172 are poorly operable. Accordingly, only skilled operators are able to perform the foregoing operative method properly. It takes a very long time for operators to attain proficiency in the operative method using the endoscope.
Studies have been made to solve such problems by applying remote-controlled robots, such as master/slave manipulators, to the medical field. The remote controlled robot is a robot system including a master arm to be operated by an operator, and a slave arm to act on a diseased part. The master arm and the slave arm are completely separated. Electric signals representing commands provided by operating the master arm are given to the slave arm. Usually the master arm and the slave arm are articulated arms having at least six degrees of freedom of motion. The master/slave manipulator is provided with controllers for controlling slave arms for operations in six degrees of freedom of motion and is a complicated system including many electric control systems, many parts and many wiring lines. Because of its complexity, the reliability of operations of the master/slave manipulator is not on a satisfactorily high level. The master/slave manipulator is a large-scale system, expensive and needs a high maintenance cost. The operator operates the master/slave manipulator at a position remote from the patient and hence the operator is unable to give medical treatment quickly to the patient in an emergency.
The inventors of the present invention proposed a medical manipulator shown in FIG. 26 in Jpn. Pat. App. No. Hei 11-165961. As shown in FIG. 26, this previously proposed medical manipulator includes an operation command unit 20 including a attitude adjusting unit 23 and an end effector control unit 24, a connecting unit 30 having one end connected to the operation command unit 20, a working unit 10 connected to the other end of the connecting unit 30 and provided with an end effector 14 and support units 15 and 16 supporting the end effector 14 for operations in at least two degrees of freedom of motion, and a controller, not shown, capable of transmitting an operation command provided by the attitude adjusting unit 23 to the support units 15 and 16 to adjust the attitude of the end effector 14 and of transmitting an operation command provided by the end effector control unit 24 to the end effector 14 to operate the end effector 14. In the working unit 10 and the operation command unit 20, the support units 15 and 16 have a pitching shaft and a yawing shaft, respectively, and the end effector 14 is a gripper.
Referring to FIG. 27, when the medical manipulator is used for suture, the end effector 14 grips a curved suture needle 180 threaded with a thread 181, sticks the suture needle 180 into a part to be sutured and moves the curved suture needle 180 along a circular path. Since required operations and the degree of freedom of motion are not properly coordinated in the known medical manipulator shown in FIG. 26, the operation command unit 20 is unable to operate smoothly for operations in directions intended by the operator. Thus, the operability of the known medical manipulator is unsatisfactory. When the working unit 10 and the operation command unit 20 are in some positions, respectively, the degree of freedom of motion of the end effector 14 is reduced, the end effector 14 is set in a singular attitude and the operability of the end effector 14 in particular directions becomes unsatisfactory. Moreover the gripping force of the end effector 14 is insufficient.